Role of diagnostic tests in the decision to perform the oral food challenge test

Background: The oral food challenge test (OFC) represents the gold standard for the diagnosis of food allergy (FA). It is also necessary for the safe reintroduction of the allergen into the diet of the patient. However, it is burdened with serious side effects. We aimed to determine the role of Skin Prick Tests (SPT) and of component resolved diagnosis (CRD) in the decision to perform OFC in patients aged between 0 and 18 years with FA towards tree nuts, peanuts and seeds. Material and Methods: We enrolled 22 patients (mean age of 10.91±4.22 years; 12 males) with a diagnosis of FA towards nuts, peanuts and seeds. A total of 29 OFCs were performed (6 of these patients were tested for more than one allergen at different times) with the following allergens: peanut, hazelnut, walnut, almond, pistachio and sesame. For each patient, were performed SPT and IgE levels through CRDs towards the culprit allergens (ImmunoCAP). In particular, for the first two variables we considered the diameter of the wheels for the allergen tested for OFC (Prick-OFC) and the mean diameter of the wheals for the other untested allergens (Prick-non OFC). For the other two variables, we focused on the IgE towards the CRDs characterizing the allergens of which they were diagnosed and tested at the OFC (CRD-OFC) and the two most cross-reactive CRDs with the first chosen CRD (CRD-cross). We conducted an inferential statistical analysis with the aim of answering the question: is it possible to predict OFC outcome using the values of the four covariates CRD- OFC, CRD-cross, Prick-OFC and Prick-non OFC? The discriminative power of each of the four covariates was first analyzed independently of the others, by performing a T-test on the two groups for each of them (Y=1, OFC positive result and Y=0, OFC negative result), figure 1. Results: The most indicative variables of a possible positive reaction to OFC are the values of the CRD-cross (p =0.01957) and of the Prick-OFC (p=0.046936), while the prick-non OFC (p=0.30857) and CRD-OFC(P=0.24193) variables do not seem to have discriminatory power. Multivariate logistic regression analysis indicates that none of the four variables considered is statistically predictive of test result. Conclusions: These results are unable to quantify the likelihood that a patient will have a positive OFC based on their SPT and IgE assays. However, we can qualitatively say what to expect by considering its CRD-cross and Prick-OFC values rather than those of CRD-OFC and Prick-non OFC.